Hot gas refrigeration system



July 25, 1961 A B. NEWTON 2,993,341

HOT GAS REFRIGERATION SYSTEM Filed Feb. 5, 1958 I 5 Sheets-Sheet 1 IN lE N TOR BWQWMW/ZWYW ATTORNEYS. r u W July 25, 1961 A. B. NEWTON2,993,341

HOT GAS REFRIGERATION SYSTEM Filed Feb. 3, 1958 5 Sheets-Sheet 2ATTORNEYS.

July 25, 1961 A. B. NEWTON 2,993,341

HOT GAS REFRIGERATION SYSTEM Filed Feb. 5, 1958 5 Sheets-Sheet 3ATTORNEYS.

This invention relates to an improvement in a hot gas refrigerationsystem, and more particularly, to a hot gas refrigeration systememploying a thermo compressor.

This application is a continuation-in-part of mycopending applicationSerial No. 663,204 filed June 3, 1957, now Patent No. 2,909,902, October27, 1959.

In the operation of hot gas refrigeration systems employing a thermocompressor, a distinct problem has arisen where the same fluid isemployed as both the refrigerant and the energy producing gas. Thethermo compressor heats the energy producing gas to an elevatedtemperature while the refrigerant operates at a reduced temperature.Providing a fluid that is stable at both of these extremes is a problemof long standing in the art. Particularly in the phase of the systemwhere the fluid is subjected to high temperatures do problems arise.Many fluids currently employed as refrigerants lack the nec essaryqualities for optimum operation in this phase. It is to be appreciatedthat because of the high temperatures employed in a thermo compressor,correspondingly high pressures are attained. Such being the case, it isof vital importance that the fluid be non-toxic since the chances offluid escape are greatly magnified. Still further, the high temperaturespromote decomposition of many fluids so that stability and resistance toexplosion is a prime prerequisite in a fluid employed for this purpose.

Another desirable characteristic of a fluid to be employed in a systemof the character described above is that it should always be at atemperature and pressure above the critical point while in the hotportion of the thermo compressor.

It is an object of this invention to provide an improvement in a hot gasrefrigeration system that overcomes the problems set forth above.Another object is to provide an improved hot gas refrigeration systemthat possesses the desirable characteristics above described.

This invention is based in part upon my discovery that carbon dioxideuniquely possesses the characteristics necessary for optimum operationof a hot gas refrigeration system employing a thermo compressor.

This invention will be explained in conjunction with the accompanyingdrawing, in which- FIGURE 1 is a representation of a refrigerationsystem, the thermo compressor portion thereof being shown in section,and the remainder schematically;

FIGURE 2 is a view similar to FIGURE 1 in that a thermo compressor isshown in section and the remaining portion of the refrigeration systemshown schematically but in which a modified form of thermo compressor isdepicted;

FIGURE 3 is a view similar to FIGURES 1 and 2 but which employs yetanother form of thermocompressor; and

FIGURE 4 is a schematic representation of a two-stage thermocompressorof the type shown in FIG. 3.

Referring now to the drawing, and in particular, FIG- URE 1, the letterA designates a casing which is divided into an upper power chamber and alower work chamher by the transverse partition wall A. Extending belowthe bottom wall of the casing is a conduit part A which forms a suctionmanifold. The upper portion of the casing is formed in two parts, whichmay be secured together by bolts 1. Within the casing are two sets ofpistons, one of which provides power in the upper chamber, and the otherof which provides for the compressing ittes atent ice of a refrigerant.Power is supplied by pistons 2, 3 and 4, While refrigerant is compressedby the pistons numbored 5, 6 and 7. Each of the pistons operates in achamber formed by casing walls, as illustrated in the drawing. The pairsof pistons 2 and 5, 3 and 6, 4 and 7, are each inter-connected byconnecting rods 8, 9 and 10, respectively. Power thus transmitteddirectly from a power piston to a compressor piston. In addition eachconnecting rod is connected to a crankshaft M on which are locatedeccentrics (or cranks) which by means of connecting rods 12, 13 and 14provide for the transmission of power from one set of pistons toanother, and for their proper cycle relationship.

The power-producing cycle similar in operation to the more or lessconventional hot air engine except that it employs a hot refrigerantgas. Heat is applied by means of burners 15 to the heads of eachcylinder l6, l7 and r18. Below the heated area of each cylinder,regenerator sections 19, 20 and 21 are provided, together with crossconnections or passages 19a and 20a so that the upper space above eachpiston is cross-connected to a lower space below an adjacent piston inthe following order: 2 to 3, 3 to 4, and 4- to 2. The chamber 18 isconnected to chamber 1 6 by means of a conduit 16a. The engine operateson a cycle comparable to hot air engines with the exception thatrefrigerant under pressure is used in place of air as the powerproducing medium.

Associated with each combination cylinder space is a small low capacitypiston driven through the medium of an eccentric on the main crankshaftor rockshaft 11. These pistons are located in cylinders so thatrefrigerants from the refrigeration portion of the system may be pumpedinto the engine portion. They may employ a limited compression ratiowhich will automatically limit the increase in pressure in the enginesection as compared to the refrigeration section. The pistons aredesignated by the numerals 22, 23 and 24. Above the pistons are passagesconnecting the piston chambers with the regenerator sections 19, 20 and21 through the valve means 22a, 23a and 24a which are effective inpermitting refrigerants to flow into the engine section but whichoperate to prevent refrigerants from returning to the lower orcompression portion of the structure. Each piston is equipped with aconventional suction valve (designated 22c, 23c and 240, respectively)which permits the flow of refrigerant from the lower refrigerant chamberinto the work chamber, while preventing return flow into the refrigerantchamber. In the drawing, the eccentrics for operating the pistons 22, 23and 24 are designated by the numerals 22b, 23b and 24b.

The limited compression ratio of the pistons 22, 23 and 24 may be usedto limit the power of the engine by means of limiting the pressure inthe power piston chambers. However, it is sometimes advantageous tooperate the refrigeration cycle at less power input, and furthermore, analternate manner of limiting the maximum power may be employed asfollows:

A pressure limiting device 25 normally urged inwardly by spring 25a, isassociated with bleed tubesr26, 27 and 28 so as to close the same, or,at a given pressure in the power chamber, to release refrigerants sothat refrigerant is bled out of the tubes into the water cooledcondenser 29 of the refrigeration system. The pressure at which thisaction occurs may be varied, as for example, by the use of temperatureresponsive bulb 30 which is responsive to the temperature in therefrigerated or air-conditioned space, and additionally, if desired, byan outside temperature responsive bulb 31 which serves to increase thecapacity during periods of warm weather or decrease it during periods ofcool weather. Other means of eifecting the bleed pressure may also beemployed such, for example,

a reduction in pressure within chambers 16, 17 and 18.

A conventional refrigeration system is operatively associated with unitA, consistingof evaporator 32, suction manifolds 33, and dischargemanifolds 34 communicating through a conduit indicated by the line 34awith the condenser 29. Flow of refrigerant occurs from condenser 29through expansion valve 36 into evaporator 32, thence back to thecompressor A for cyclic return to the refrigeration circuit throughcondenser 29. Thus, it is apparent that the same fluid circulates in therefrigeration cycle as in the power cycle.

The system may be started and stopped by means of a conventionalthermostat 39 which operates through limit controls such as 49responding to high refrigerant temperature and 41 responding to highengine temperature. Assuming that a demand for cooling has existed forsome time, thermostat 39 will maintain valve 42 in an open position,allowing fuel to enter the burner and heat the engine chambers 16, 17and 18. To further such heating, fins, as indicated by the numeral 43,may be employed. The flue gases may be expelled through one or moreflues, 44, 45, etc. Furthermore, the gas may be lighted and controlledsafety-wise by a conventional pilot, as at 46.

Provision is made for re-starting the engine after shutdown, and thisprovision is associated with the action at the time of shutting down.When the thermostat 39 is satisfied, it closes valve 42 andsimultaneously, by means of a combination relay and timer 47, closesvalve 35 and opens valve 48. The liquid refrigerant is then divertedfrom the expansion valve 36 into auxiliary receiver 49 during thecool-down or coasting period of the engine. The refrigerant enters checkvalve 50 (the use of which is optional), and receiver 49 may be suppliedwith a relief device 51 so that in the event excessive pressure isdeveloped, the refrigerant will relieve or flow back into thewater-cooled condenser 29 in sufficient quantity to remove the pressurehazard. During the coasting period of the engine, the refrigerant,carbon dioxide, can be accumulated in receiver 49 either as a liquid oras a super-critical gas. That this is possible can be appreciated fromthe fact that the critical temperature for carbon dioxide is within therealm of room temperatures and because the shape of the constanttemperature and constant pressure lines on the T-S diagram make thesequence of pressure change during starting the same whether the carbondioxide is accumulated as a liquid or as a gas.

When the thermostat again calls for an operation of the equipment, itopens valve 42 to ignite the main gas burners 15. It also opensauxiliary gas valve 52 to ignite burner 53, thus applying heat toauxiliary receiver 49. Valve 54 is also opened at the same time so as toapply higher pressure refrigerant to chamber 55. In chamber 55 is a disk55a rotatably mounted on the main crankshaft 11 and provided with avalve passage 55b sequentially registering with tubes 56, 57 and 58, andcommunicating also with the space 550. This disk acts as a valve forpermitting successive flow of refrigerant into the tubes for startingthe operation of the pistons as the transverse opening 55b is broughtsequentially into registry with the tubes. The rise of pressure broughtabout by the flow of highly heated refrigerant through the tubes startsthe movement of the pistons, which is immediately augmented by the risein pressure of the next appropriate space as well as by the heat inputfrom the main burner 15. The combination of relay timer 47 soon closesvalve 52 and somewhat later closes valve 54, and the engine thencontinues to operate under the heat input of the main burner 15.Alternately, the speed of rotation of the engine may be used to closevalve 52 and valve 54 rather than the timing action of a relay such as47.

Certain other pieces of equipment, such as fans and pumps, mayfrequently have to be operated in conjunction with refrigerantapparatus. This can be done by themain engine in the obvious manner ofproviding a shaft seal for crankshaft 11 and appropriate driving meansexternal to the engine for fans, pumps, etc. However, an alternatemethod is shown in which a turbine or positive displacement engine 59drives apparatus such as fan 60 or pump 61. This engine 59 obtains itsenergy from the high pressure refrigerant line 34a through valve 62shown controlled by governor 63. This means for driving such auxiliarymechanism is provided without the necessity of using electricalconnections of any kind, and even though this is accomplished in therefrigerant portion of the cycle, the low cost of fuels used for directfiring permits this action without excessively burdening the system withcost of operation.

In the operation of the foregoing structure, the use of carbon dioxideinstead of a noncondensible gas, such as air, permits one to takeadvantage of a partial condensation cycle, if so desired. This isaccomplished by adjusting the pressure levels in the chambers 16, 17 and18, as controlled by the controller 25, to a point in which some of therefrigerant condenses as it passes through regenerator 19, 20 or 21 intothe corresponding cold space below. This causes a marked furtherreduction in volume while raising the mean effective pressure. As thecombined remaining gas and condensed refrigerant is forced back throughthe regenerator, the condensed refrigerant is re-evaporated as thecondensed refrigerant comes into intimate contact with the heatedexchanger. By control of the pressure in chambers 16, 17 and 18, it isthus possible to operate above the critical temperature of therefrigerant during the hot portion of the cycle and below the criticaltemperature during the cold portion of the cycle, in each set ofchambers. This yields a mean effective pressure greater than thatachievable in a cycle which did not cross the critical point.

Carbon dioxide is particularly adapted for operation in the engine andcompressor system above described. Carbon dioxide has sufiicientstability at the elevated temperature in the hot end of the cylinderwhile always being at a temperature and pressure above the criticalpoint, at the same time being effective as a refrigerant in theoperation of the refrigeration system. .For these reasons, and others,carbon dioxide appears to be unique as a combined refrigerant and energyproducing gas in the thermo compressor of hot gas systems. Carbondioxide may be effectively employed for operation in the power cycle onboth sides of the critical pressure. In fact, with sufficient cooling ofthe bottom end of the cylinder, there can be easily a zone ofcondensation which will limit the high pressure attainable by heatinggases in the hot end of the cylinder, whereby some of the energy istransferred directly from the heat input at one end of the cylinder torefrigerant at the other end of the cylinder. Putting the matter inanother way, the carbon dioxide compresses itself in thethermocompressor and then expands through an expansion valve in theevaporator without ever being subjected to an external power cycle, andin this operation the carbon dioxide has peculiarly excellentcharacteristics and is unique.

In FIGURE 2 of the drawing, a modified form of thermocompressor isdesignated generally with the letter B and the refrigeration system inwhich it is employed is designated generally with the letter C. Therefrigeration system C is for the most part conventional, and provides acondenser and an evaporator coil 111, connected together through aconduit 112 having an expansion valve 113 interposed therein. A conduit114 leads from the evaporator 111 to a manifold 115 through a pressureregulator valve 116, the inclusion of which in the system is optional.The condenser 110 is connected through a conduit 117 with a manifold118. The condenser 110 is cooled by a Water coil 119 mounted in heatexchange relation therewith and that is" connected through a conduit 120and control valve 121 with a source of water (not shown). Preferably, abypass conduit 122 provided with a control valve 123 bypasses thecontrol valve 121, and this bypass is utilized in initiating arefrigeration cycle in a manner that will be described hereinafter. Itmay be noted that a capillary tube 124 is connected at one end with theexpansion valve 113 and at its other end is equipped with a thermallysensitive bulb in heat exchange relation with the flow conduit 114.

The compressor B is equipped with at least one cylinder, and preferablya plurality of cylinders. In the illustration of FIGURE 2, two cylindersare shown, and since these cylinders and their associated parts areidentical in construction, only one will be described; and for purposesof identification cylinders and their associated components will bedesignated by the letters a and h following each numeral. Specificallythen, the cylinder on the left in FIGURE 2 will be designated with thenumeral and letter 125a while the cylinder on the right will bedesignated as 125b. Mounted for reciprocatory motion within thecylinders are the pistons 126a and 12612.

Mounted below the cylinder is a crankcase 127 that is mounted forrotation therein upon the bearings 128 and 129 and a crankshaft 130 thatmay be rotatably supported intermediate the ends thereof in a mainbearing assembly 131 suitably supported or secured to the casing 127.The crankshaft 130 is coupled to the pistons 126a and 1261) respectivelythrough the connecting rods 132a and 13212, and the piston rods 133a and133b. At their upper ends the piston rods are secured to the pistons andat their lower ends are secured at the joints 134a and 134b to theconnecting rods in a conventional manner as are the connecting rodssecured to the crankshaft. Thus when the crankshaft is rotated, thepistons are reciprocated in their cylinders.

Preferably, a low energy power source is employed for rotating thecrankshaft 130 so as to reciprocate the pistons within their cylinders.Since the energy for compression is obtained from means to besubsequently described and that is apart from the power source, onlysufiicient power need be provided to the crankshaft 130 for overcomingthe friction of the moving parts and for overcoming whatever frictionmay appear as refrigerant flows from one end to the other end of thecylinders and over the reciprocable distance therein. A number ofdifferent arrangements might be provided for reciprocating the pistonsthrough rotation of the crankshaft 130; and one example arrangement isillustrated in FIGURE 2.

Shown in FIGURE 2 is a small motor 135 having a driving member 136 fixedto the shaft 137a thereof. The driving member 136 is semi-cylindricaland receives therein an armature 137 that is directly connected to thecrankshaft 130. As the motor 135 rotates, the driving member 136 isrotated and thereby causes the armature 137 to rotate which then in turndrives the crankshaft 130. The members 136 and 137 might be a magneticclutch, or if desired, the number 136 could be the field windings of amotor while the number 137 could be the rotor of the motor.

It is desired to provide the crankcase 127 as a sealed unit and for thispurpose a seal member 138 is provided about the rotor 137. The member138 is sealingly secured to the casing 127 and is preferably formed'of anon-magnetic material that will not interfere with the operation of thedriving member 136 and the rotor 137. It will be apparent that alubricant will ordinarily be provided within the crankcase chamber 139for lubricating the crankshaft 130, as well as the connecting rods 132aand 1321) and the piston rods 133a and 133k. Lubricant is not requiredwithin the cylinders 125a and 125k and, therefore, the piston rods 133aand 133b, where they eX- tend through the bosses 140 and 141 of thecasing 127, are preferably provided with packing glands so as to preventthe admission of lubricant from the crankcase chamber-139 and into thecylinders.

Provided about the upper end portions of the cylinders 125a and 125b isa casing 142 that is rigidly secured to the cylinders at approximatelythe mid-portions thereof. The casing 142 is provided with spaced-apartopenings 143 and 1144 through the top wall thereof that are inalignment, respectively, with the upper ends of the cylinders 125a and125b. A manifold 145 adapted to be secured to a source of combustiblegas through a control valve 146 is equipped with burners 147 and 148that are aligned, respectively, with the upper ends of the cylinders125a and 1125b. About the burners 147 and 148, the casing 142 providesan inwardly-tapered annular flange 149 equipped at its lower end with anoutwardly-extending annular skirt 150. The casing provides a similarflange 151 and skirt portion 152 about the burner 148. The burnersfunction in a conventional manner to burn a combustible fuel suppliedthereto, secondary air for combustion entering the casing 142 throughthe apertures 143 and 144, and primary air being entrained in the fuel.The casing 142 is provided with an exhaust port 153 through which theproducts of combustion are removed from the chamber defined by thecasing 142. It is to be appreciated that either the combustion air orthe gas itself may be preheated by heat exchange with the flue gases inorder to even further improve the efficiency of the system described.

While the upper end portion of the cylinders are heated, the lower endportions are cooled. To accomplish this result, preferably cooling coils154a and 154b are provided, respectively, about the cylinder ends, andthese coils are connected together in series by a conduit 155. Liquidfor cooling the cylinders is supplied to the coil 154 b through theconduit 156 that is connected with the cooling coil 119 and thecondenser 110. The liquid, which ordinarily will be water, may bedischarged to waste through the outlet conduit 157 that is connected tothe coil 154a. While the cooling coils are shown connected in series, itwill be appreciated that a parallel arrangement might be provided,although ordinarily a series waterfiow path will be preferable.

To facilitate heat exchange with a refrigerant within the cylinders 125aand 125b, the upper end portions of these cylinders are provided withexternal fins 158a and 1531). Each of the cylinders internally isprovided with internal fins 159a and 15% that extend longitudinally ofthe cylinders. The internal heat exchange fins are oriented about thecylinder in spaced apart relation, and overlapping the same inintermeshed and nesting relation therewith are the external fins 1611aand 16% that are provided by each of the pistons. The pistons are freelyfitted within the cylinder so that they reciprocate therein withoutengagement between the internal and external fins being provided.Therefore, fiuid within the cylinder is free to pass from one end to theother end thereof as the pistons reciprocate. Preferably, the cylindersand their pistons are cylindrical throughout the central portionthereof, and as shown in FIGURE 2, and have end sections attachedthereto of conical configuration.

At their lower ends, the cylinders are provided with ports arranged toproduce a two-stage compression. Cylinder 125b communicates withmanifold through a port 16115 in which is positioned a control valve162b, the cylinder a having an inlet port 161a. Similarly, each of thecylinders is provided respectively with outlet ports 163a and 16312. Theoutlet port 16% of cylinder 125bcommunicates with outlet 161a ofcylinder 125a through valve 164]). In this arrangement the second stagecylinder needs no inlet valve. An outlet valve 164a controls flow fromcylinder 125a to manifold 118. Refrigerant is admitted into the lowerend portions of the right-hand cylinder 1251: through an inlet port thatcommunicates with manifold 115, which in turn communicates with theconduit 114 and evaporator 111. Compressed refrigerant is expelled fromthe left-hand cylinder 125a through the discharge port that communicateswith the manifold 118, which in turn is connected to the condenser 115In the operation of the apparatus, it is necessary to initiate rotationof the compressor, ignition of the burners, and start of water flow.These may occur simultaneously or in any sequence suitable for a givenengine. For example, the motor 135 can be first energized to rotate thecrankshaft 130 and to reciprocate the pistons 1216a and 12Gb Withintheir respective cylinders. At approximately the same time, the controlvalve 146 is opened to supply combustible gas to the burners 147 and14-8 which are then ignited. The auxiliary water control valve 123 isthen opened to permit water to flow through the coil 119 to cool thecondenser no and also permit the water to flow through the cooling coils154a and 1514b to cool the lower end portions of the cylinders. Thepurpose of the by-pass 122 and its flow control valve 123 is to assurethat a relatively small amount of water will flow initially while therefrigerant cycle is placed in operation, the purpose of this waterbeing to cool the lower end of the cylinders during the startingprocedure. With these steps taken, the upper end portions of thecylinders are heated while the lower end portions thereof are cooled,and at the same time the condenser 110 is cooled. If the mass is veryhigh in cylinders 125a and 125b, it might be desirable to start heatingthe cylinders first, followed by water flow and then compressorrotation. This sequence has been found particularly applicable whencarbon dioxide is employed as the refrigerant.

Energizing of the motor 135 causes the pistons to reciprocate withintheir cylinders, and such reciprocation causes a displacement of therefrigerant carbon dioxide within their cylinders, first from one endthereof to the other, and thereafter to the first end. Reciprocation ofthe pistons causes cyclic repetition of this fluid flow or fluiddisplacement within the cylinders. In one position of the pistons,refrigerant is drawn into the cylinders from the evaporator 111, andafter the compression of that refrigerant and following a reciprocationof the pistons", the fluid is discharged through the outlet ports and ispumped into the condenser 110.

In the position of the pistons as is shown in FIG. 2, the piston 126a isin substantially its uppermost position within its cylinder, While thepiston 12611 is in its lowermost position within its cylinder. Assumingthe positon of piston 126a, the cavity of the cylinder 125a beneath thepiston is filled with cool carbon dioxide that has been admitted throughthe cylinder 125b which has performed the first stage of compression. Asthe piston 126a moves downwardly to fill the cylinder cavity therebelow,it displaces the cold carbon dioxide and causes it to flow upwardly inheat transfer contact with the internal fins 159a of the cylinder andthe external fins 160a of the piston. The fins are progressively warmertoward the top of the cylinder, and as the refrigerant flows upwardly,the temperature thereof is raised, and correspondingly its pressure israised so that a portion of the refrigerant carbon dioxide in expandedcondition is forced outwardly through the discharge valve 164a and thedischarge port 163a and into the manifold 118, and from there into thecondenser 110.

To permit the achievement of maximum efliciencies, it may be desirableto increase the displacement of the first stage cylinder. This can bedone by making the diameter or stroke, for example, of cylinder 12517greater than that of cylinder 125a. V

Stated another way, the refrigerant gas leaves and enters the cylinderfrom the cold end there of. The gas entering the cylinder from theevaporator is cooled and must be heated many hundreds of degrees in' theupper end of the cylinder toincrease the pressure. Discharging it atthis high temperature into the condenser would require a very muchoversize condenser, and to avoid this, the carbon dioxide is dischargedat the bottom of the cylinder, and it is important that the portion ofthe gas which is discharged has never been heated, or, if it waspartially heated, becomes cooled as it flows past the fins on the pistonand cylinder.

7 Referring now to the cylinder 12517 in the position of the piston 126btherein, the major volume of the carbon dioxide refrigerant in thatcylinder is in the hot end thereof, and is thereby heated to a hightemperature since the upper end portion of the cylinder is heated by theburner 148. Thus, the pressure of the heated refrigerant will increase.As the pressure increases, refrigerant carbon dioxide is forced out ofthe cylinder through the discharge port 1639b and its discharge valve16% into cylinder a. As the piston 126b rises in its cylinder, theheated refrigerant is displaced to the cool end of the cylinder, and itsmovement passes in heat transfer contact with the internal fins 15% ofthe cylinder and the external fins 16011 of the piston. Since thesepistons are progressively cooler toward the cold end of the cylinder,the refrigerant is cooled thereby as it flows thereover. It will beappreciated that the fins 16Gb of the piston are progressively coldertoward the bottom end thereof because those fins have been cooled bydirect heat transfer at the cold end of the cylinder during the time thepiston is within the lower or cooled end portion of the cylinder. Duringthe time the refrigerated carbon dioxide is transferring to the cold endof the cylinder, the refrigerant is cooled and the pressure thereof isreduced until a sufficiently low pressure is reached to open the suctionregulating valve 116, and refrigerant will then be drawn in from theevaporator 111 and the evaporator will be cooled by this movement of therefrigerant.

This cyclic operation is carried on repetitiously, with the result thatthe temperature changes within the cylinder 125 b serve to draw suctionrefrigerant in through the suction valve 162!) and to discharge itthrough the discharge valve 16% tocylinder 125a, which dischargesrefrigerant back to the condenser. Thus, the heat energy of the burners147 and 148 is transferred directly into the compression oftherefrigerant canbon dioxide through the utilization of the extremelysmall amount of power which is supplied by the external power source orspecifically the motor 135. Actually, the only power that needs besupplied by the external power source is that which is suflicient toovercome the friction of the mechanical components and of the flow. ofthe refrigerant carbon dioxide past the pistons 126a and 12612.

There is a gradual change in temperature from the hot end portions ofthe cylinders to the cold end portions thereof. This temperaturegradient is constantly maintained so that the heat transfer may beaugmented by the fins, as described. In addition, the moving fins, orthe fins provided by the pistons 126a and 12611, serve as movingregener'ators with respect to the refrigerant carbon dioxide, and asheat transfer units which alternately come in contact with the cold andhot end portions of the cylinder for further facilitating heat transfer.

The degree of cooling of the lower end portions of the cylinders 125aand 1251) may be varied as desired. Variations may be provided bycontrolling the volume of liquid flowing through the coils 154a and 154k(which are in good heat exchange relation With the cylinders and arepreferably in contact therewith), and might also be provided by varyingthe temperature of the liquid flowing therethrough. The greater theamount of cooling of the lower end portions of the cylinders, thegreater will be the tendency for some of the refrigerant carbon dioxideto condense within the lower portions of the cylinders. However, no harmwill be done by such condensation, and in the most extreme case wherethe lower end portions of the cylinders are cooled to a very lowtemperature, all of the condensation of the refrigerant may occur withinthe cylinders; This is possible since clearances between the sidesof thepiston and the cylinder are such as to provide passages for the escapeof any liquid which would be inadvertently trapped at the end of thepiston stroke. In this case, the condensed refrigerant may be removedfrom each cylinder as it condenses during the compression stroke.

Yet another form of thermocompressor in a conventional refrigerationsystem and which provides extremely satisfactory results when carbondioxide is employed as both the energy producing gas and refrigerantfluid, is shown in FIG. 3. In FIG. 3, the letter D designates generallya thermocompressor, while the letter E desig- ,nates a refrigerationsystem. The refrigeration system designated by the letter E includes acondenser 210, an expansion valve 211, and an evaporator 212, allconnected in series through conduit 213 through which flows therefrigerant carbon dioxide. Also interconnected in conduit 213 isrefrigerant-distributing valve 214 which is coupled to evaporator 212through port 215. Valve 214- is coupled to the conduit communicatingwith condenser 210 through port 216 and with thermocompressor D throughconduit 217 and port 218. High pressure carbon dioxide withinthermocompressor D flows into chamber 219 of valve 214 and opensdischarge valve 220 while closing intake valve 221. This permitsrefrigerant to flow into condenser 21%. Refrigerant from condenser 210flows to evaporator 212 and then reenters thermocompressor D by passingthrough intake valve 221.

The thermocompressor unit D is provided with a closed compressorcylinder 222 having an upper hot end of conical or other surface ofrevolution for conducting large amounts of heat from a burner 223 to theinterior of the cylinder 222. As in the structure shown in FIG. 2, thecompressor cylinder 222 may be provided with fins to aid the transfer ofheat from burner 223 to the interior of cylinder 222.

The lower cold end or head of cylinder 222 has a water jacket 224 havingan inlet 225 and a discharge port 226. Water for this purpose may beconveniently taken from condenser 21%, as indicated at 210a, the flowrate of water in condenser 210 being regulated by a pressureresponsivevalve 21Gb in the refrigerant line between valve 214 and condenser 21%).Valve 21Gb actuates valve 210a in the water supply line 210d tocondenser 210, the valve 2100 being provided with a conventional by-pass210a. The central portion of cylinder 222 is equipped with a heatregenerator 227 provided with passages for the flow of gas. A cylinderliner 22% is concentrically placed within cylinder 222 and spaced with anarrow gas passage 229 leading from the upper hot space 230 throughregenerator 227 to the bottom cold space 231. A gas-moving or transferplunger 232 is reciprocably mounted within cylinder 222 and has its endsconstructed to conform with the ends of cylinder 222 and the cylinderliner 228, the plunger 232 operating in close approximation to cylinderliner 228 but without touching the same. The stroke of the transferpiston 232 is controlled by piston 233, piston rod 234, connecting rod235, crank 236, shaft 237, and flywheel 238.

The piston 233 serves to furnish the power to operate the compressor byutilizing the variation of pressure in the compressor cylinder 222, asis hereinafter discussed. A surge chamber 239 communicates with the bore240 which receives piston 233. Surge chamber 239 serves to furnish powerfor the suction stroke by storing. the excess power from the compressionstroke. Thus, the embodiment presented in FIG. 3 provides an alternativemeans for moving the piston in a thermocompressor as compared to themotor 135 shown in FIG. 2.

As transfer piston 232 moves from the hot space 230 to the cold space231, it displaces the cold carbon dioxide from space 231 through theregenerator 227 and annular space 229 to the hot space 236. During thistransfer, the gas is heated by the regenerator 213 and the hot cylinderwalls, the heat being derived from burner 223. This latter heating isassisted by the narrow annular space 229 between cylinder 222 and liner228. The heating of the gas raises the pressure until the back ordifferential pressure valve 214 opens. Thereafter, as pointed out above,the pressure remains constant while gas is being discharged throughdischarge valve 220 to refrigeration system E. On the return or suctionstroke, the hot gas in the space 230 flows through the annular space 229and regenerator 227 to the cold space 231 leaving heat in regenerator227 and being further cooled by the water jacket 224. This cooling ofthe gas causes the pressure to fall during the first part of the strokeand then the pressure remains constant while the gas flows fromevaporator 212 through intake valve 214 to the cold end 231 ofcompressor cylinder 222. Since the pressure in cylinder 222 rises duringthe first part of the compression stroke and remains high during thelatter part of the stroke while it falls during the first part of thesuction stroke and remains low during the latter part of the suctionstroke, the mean pressure on the compression stroke is higher than themean pressure on the suction stroke.

If no refrigerant is taken from evaporator 212, the discharge from thecompressor continues to decrease and the compressor would stop exceptfor the fact that the piston 233 has two reduced sections 241 and 242which act as ports for the transfer of gas from the cylinder 222 to thesurge tank 239. If the valve 243 in conduit 244 is opened when reducedsection 241 moves adjacent to the top port of by-pass line 244 at theend of the compression stroke, the high pressure gas in cylinder 222flows through the by-pass conduit 244 to the surge tank 233. On thereturn or suction stroke, the high pressure gas in surge tank 239 actson piston 233 to overcome the more rapidly falling pressure in section222 and also furnish power to operate the compressor. At the end of thesuction stroke, the reduced section 242 moves adjacent to the port ofby-pass conduit 244, allowing the high pressure gas in surge chamber 239to flow into cylinder 222 so that on the compression stroke the rapidlyrising pressure in cylinder 222 serves to compress the gas in surgechamber 239 and furnish power to operate the compressor. By adjustingthe manually-operable valve 243, the idling speed of the compressor maybe controlled. When the refrigerant gas is drawn from the evaporator212, the thermocompressor speed automatically increases to meet theincreased demand. The thermocompressor thus serves as a self-containedunit.

It is tobe appreciated that the thermocompressor of FIG. 3 can besupplemented by a second cylinder to pro vide a two-stage compressioncycle of the nature seen in FIG. 2.

In FIG. 4, a schematic representation is given of a modified form of hotgas refrigeration system employing the type of thermocompressor shown indetail in FIG. 3. For that reason, it is believed unnecessary to showthe system in detail. In FIG. 4, the letter F designates athermocompressor of the type shown in FIG. 3 and designated by theletter D. In FIG. 4, the letter G designates a second suchthermocompressor, the two compressors being interconnected in seriesthrough a valve designated by the numeral 314 and which is similar tovalve 214 of FIG. 3. In FIG. 4, a conduit line 313 interconnects valve314 with an evaporator 312. A second conduit 316 connects valve 314 withthermocompressor G, while conduit 317 connects valve 314 withthermocompressor F, much the same as conduit 217 communicates valve 214with thermocompressor D in FIG. 3. A second outlet port is provided inthermocompressor G and is interconnected through line 345 with a valve346 such as a float or expansion valve. Valve 346 in turn is connectedto evaporator 312. It is preferred to locate valve 346 as close aspossible to thermocompressor G so as to keep the clearance volume at aslow a value as possible. Cooling jackets are provided thermocompressorsF and G, similar to the jacket 224 of FIG. 3 and cooling water is sentthrough the staged thermocompressors F and G in countercurrent flow,-i.e.,

. 11 first to thermocompressor G and then to thermocompressor F.

As in the embodiment of the invention illustrated in FIG. 2, it ispossible to obtain maximum efliciency of operation through providing adifferent displacement in the two or more cylinders making up thethermocompressor. In the embodiment of the invention shown in FIG. 4, itis possible to connect the piston of thermocompressor G to the samecrankshaft as that connected to the piston of thermocompressor F butproviding a different diameter or stroke in thermocompressor G than inthermocompressor F. Further, if a common crankshaft for the twothermocompressors is employed, it is possible to use only one drivingpiston such as piston 233. On the other hand, if separate cranks andcrankshafts are employed, each with its own driving piston, thedifferences in displacement in the various thermocompressor cylinderscan be obtained by allowing the respective pistons to travel atdifferent speeds. In this manner, the number of reciprocations per unitof time in the low stage cylinder could easily be 40% or 50% greaterthan that in the higher stage cylinder.

Valve 346 only perm-its the outflow of refrigerant from thermocompressorG to evaporator 312 when the carbon dioxide is in a liquid state. This,therefore, eliminates the need for a condenser and an expansion valvesuch as are shown in FIG. 3. Where, however, carbon dioxide is employedas the refrigerant, the critical temperature being in the range ofordinary ambient temperatures, requires cooling water sufficiently lowin temperature so as to condense all of the refrigerant. When this isunavailable, or otherwise unfeasible, an expansion valve 346 canbeemployed that is equipped with a sensing bulb 346a located in theoutlet line 313. Expansion valve 346 can thus measure the super heat inthe refrigerant circulation system and operate to allow super-criticalgas to leave thermocompressor G.

While, in the foregoing specification, embodiments of the invention havebeen set forth and described in considerable detail for the purpose ofadequately illustrating and describing the invention, it will beapparent to those skilled in the art that numerous changes may be madein these details without departing from the spirit and principles ofthis invention. i

I claim:

1. In the operation of a refrigeration system including athermocompressor, the improvement comprising condensing a refrigerant inthe thermocompressor and limiting the refrigerant discharged from saidthermocompressor to that in liquid form, whereby the need for acondenser in the refrigeration system is eliminated.

2. The method of claim 1, in which the said refrigerant is carbondioxide.

3. In a refrigeration system, evaporator means, and thermocompressormeans operatively connected to circulate a refrigerant, the saidthermocompressor means comprising a closed cylinder heated at one endand cooled at the other end, piston means reciprocably mounted in saidcylinder with flow passage means in said cylinder permitting fluid toby-pass said piston means, and conduit means communicating said cylinderwith said evaporator means, said conduit means including valve meansnormally operative to pass only liquid refrigerant whereby liquidrefrigerant is delivered from said thermocompressor means to saidevaporator means.

4. The structure of claim 3, in which said valve means is equipped withmeans responsive to the refrigerant super heat and selectively permitthe outflow of refrigerant in a super-critical gas phase from saidthermocompressor means to said evaporator means.

5. In a refrigeration system, evaporator means, and at least twothermocompressor units interconnected in series to provide stagedcompression, the said evaporator means and thermocompressor units beingoperatively connected to circulate carbon dioxide as a refrigerant,conduit means communicating one of said thermocompressor units with asecond of said thermocompressor units and said evaporator means, andsecond conduit means including valve means communicating the said sec-0nd of said thermocompressor units with said evaporator means.

References Cited in the file of this patent UNITED STATES PATENTS2,272,925 Smith Feb. 10, 1942 2,468,293 Du Pre Apr. 26, 1949 2,484,392Heeckeren Oct. 11, 1949 2,621,474. Dros Dec. 16, 1952 2,721,728 HigginsOct. 25, 1955 2,734,354 Kohler Feb. 14, 1956 2,771,751 Jonkers Nov. 27,1956 2,803,951 Newton Aug. 27, 1957 2,824,430 Rinia Feb. 25, 1958 t

